/*
 * Lazy Load - jQuery plugin for lazy loading images
 *
 * Copyright (c) 2007-2011 Mika Tuupola
 *
 * Licensed under the MIT license:
 *   http://www.opensource.org/licenses/mit-license.php
 *
 * Project home:
 *   http://www.appelsiini.net/projects/lazyload
 *
 * Version:  1.7.0-dev
 *
 */
(function($) {

	$.fn.lazyload = function(options) {
		var settings = {
			threshold: 0,
			failure_limit: 0,
			event: "scroll",
			effect: "show",
			container: window,
			skip_invisible: true
		};

		if(options) {
			/* Maintain BC for a couple of version. */
			if(null !== options.failurelimit) {
				options.failure_limit = options.failurelimit;
				delete options.failurelimit;
			}

			$.extend(settings, options);
		}

		/* Fire one scroll event per scroll. Not one scroll event per image. */
		var elements = this;
		if(0 == settings.event.indexOf("scroll")) {
			$(settings.container).bind(settings.event, function(event) {
				var counter = 0;
				elements.each(function() {
					if(settings.skip_invisible && !$(this).is(":visible")) return;
					if($.abovethetop(this, settings) ||
						$.leftofbegin(this, settings)) {
						/* Nothing. */
					} else if(!$.belowthefold(this, settings) &&
						!$.rightoffold(this, settings)) {
						$(this).trigger("appear");
					} else {
						if(++counter > settings.failure_limit) {
							return false;
						}
					}
				});

				/* Remove image from array so it is not looped next time. */
				var temp = $.grep(elements, function(element) {
					return !element.loaded;
				});
				elements = $(temp);

			});
		}

		this.each(function() {
			var self = this;
			self.loaded = false;

			/* When appear is triggered load original image. */
			$(self).one("appear", function() {
				if(!this.loaded) {
					$("<img />")
						.bind("load", function() {
							$(self)
								.hide()
								.attr("src", $(self).data("original"))[settings.effect](settings.effectspeed);
							self.loaded = true;
						})
						.attr("src", $(self).data("original"));
				};
			});

			/* When wanted event is triggered load original image */
			/* by triggering appear.                              */
			if(0 != settings.event.indexOf("scroll")) {
				$(self).bind(settings.event, function(event) {
					if(!self.loaded) {
						$(self).trigger("appear");
					}
				});
			}
		});

		/* Check if something appears when window is resized. */
		$(window).bind("resize", function(event) {
			$(settings.container).trigger(settings.event);
		});

		/* Force initial check if images should appear. */
		$(settings.container).trigger(settings.event);

		return this;

	};

	/* Convenience methods in jQuery namespace.           */
	/* Use as  $.belowthefold(element, {threshold : 100, container : window}) */

	$.belowthefold = function(element, settings) {
		if(settings.container === undefined || settings.container === window) {
			var fold = $(window).height() + $(window).scrollTop();
		} else {
			var fold = $(settings.container).offset().top + $(settings.container).height();
		}
		return fold <= $(element).offset().top - settings.threshold;
	};

	$.rightoffold = function(element, settings) {
		if(settings.container === undefined || settings.container === window) {
			var fold = $(window).width() + $(window).scrollLeft();
		} else {
			var fold = $(settings.container).offset().left + $(settings.container).width();
		}
		return fold <= $(element).offset().left - settings.threshold;
	};

	$.abovethetop = function(element, settings) {
		if(settings.container === undefined || settings.container === window) {
			var fold = $(window).scrollTop();
		} else {
			var fold = $(settings.container).offset().top;
		}
		return fold >= $(element).offset().top + settings.threshold + $(element).height();
	};

	$.leftofbegin = function(element, settings) {
		if(settings.container === undefined || settings.container === window) {
			var fold = $(window).scrollLeft();
		} else {
			var fold = $(settings.container).offset().left;
		}
		return fold >= $(element).offset().left + settings.threshold + $(element).width();
	};
	/* Custom selectors for your convenience.   */
	/* Use as $("img:below-the-fold").something() */

	$.extend($.expr[':'], {
		"below-the-fold": function(a) {
			return $.belowthefold(a, {
				threshold: 0,
				container: window
			})
		},
		"above-the-fold": function(a) {
			return !$.belowthefold(a, {
				threshold: 0,
				container: window
			})
		},
		"right-of-fold": function(a) {
			return $.rightoffold(a, {
				threshold: 0,
				container: window
			})
		},
		"left-of-fold": function(a) {
			return !$.rightoffold(a, {
				threshold: 0,
				container: window
			})
		}
	});

})(jQuery);